1. Field of the Invention
The invention relates to a device for electrostatic air cleaning. The device is based on the corona discharge and ions acceleration along with dust particles charging and collecting them on the oppositely charged electrodes.
2. Description of the Related Art
A number of patents (see, e.g., U.S. Pat. Nos. 4,689,056 and 5,055,118) describe electrostatic air cleaning devices that including (i) ion and resultant air acceleration generated by a corona discharge method and device coupled with (ii) charging and collection of airborne particulates, such as dust. These corona discharge devices apply a high voltage potential between corona (discharge) electrodes and collecting (or accelerating) electrodes to create a high intensity electric field and generate a corona discharge in a vicinity of the corona electrodes. Collisions between the ions generated by the corona and surrounding air molecules transfer the momentum of the ions to the air thereby inducing a corresponding movement of the air to achieve an overall movement in a desired air flow direction. U.S. Pat. No. 4,689,056 describes the air cleaner of the ionic wind type including corona electrodes constituting a dust collecting arrangement having the collecting electrodes and repelling electrodes alternately arranged downstream of said corona electrode. A high voltage (e.g., 10–25 kV) is supplied by a power source between the corona electrodes and the collecting electrodes to generate an ionic wind in a direction from the corona electrodes to the collecting electrode. As particulates present in the air pass through the corona discharge, a charge corresponding to the polarity of the corona electrodes is accumulated on these particles such that they are attracted to and accumulate on the oppositely-charged collecting electrodes. Charging and collecting of the particles effectively separates-out particulates such as dust from fluids such as air as it passes through the downstream array of collecting electrodes. Typically, the corona electrodes are supplied with a high negative or positive electric potential while the collecting electrodes are maintained at a ground potential (i.e., positive or negative with respect to the corona electrodes) and the repelling electrodes are maintained at a different potential with respect to the collecting electrodes, e.g., an intermediate voltage level. A similar arrangement is described in U.S. Pat. No. 5,055,118.
These and similar arrangements are capable of simultaneous air movement and dust collection. However, such electrostatic air cleaners have a comparatively low dust collecting efficiency that ranges between 25–90% removal of dust from the air (i.e., “cleaning efficiency”). In contrast, modern technology often requires a higher level of cleaning efficiency, typically in the vicinity of 99.97% for the removal of dust particles with diameter of 0.3 μm and larger. Therefore state-of-the-art electrostatic air cleaners can not compete with HEPA (high efficiency particulate air) filtration-type filters that, according to DOE-STD-3020-97, must meet such cleaning efficiency.
Accordingly, a need exists for an electrostatic fluid precipitator and, more particularly, an air cleaning device that is efficient at the removal of particulates present in the air.